1. Field of the Invention
The present invention relates to an endoscope including an operation portion to which a display device for displaying an endoscope image picked up by image pickup portion is connected.
2. Description of Related Art
Conventionally, as a light source of an endoscope, well-known is a light source lamp built in a light source device as a peripheral device to which an endoscope is connected. When illumination light is supplied to an endoscope from a light source device, the illumination light emitted from a light source lamp is transmitted to a distal end of an insertion portion via from a universal cord to an operation portion of the endoscope, by means of light guide fiber extended inside of the endoscope, and then the illumination light is irradiated from the distal end of the insertion portion to a region to be inspected.
In addition, in recent years, for the purpose of simplifying a whole endoscope apparatus including an endoscope and peripheral devices, well-known is an endoscope having a configuration in which a light source is configured of a light emitting diode provided in the endoscope and a display device for displaying an endoscope image is connected to an operation portion.
Providing a light source configured of the light emitting diode in the endoscope eliminates the need for a light source device connected to the endoscope, thereby simplifying the endoscope apparatus. In addition, the light emitting diode is capable of emitting light with lower electric power compared with light source lamp and the like, thereby realizing power saving in the endoscope apparatus. Furthermore, connecting the display device to the operation portion eliminates the need for a monitor device to be separately connected to the endoscope, thereby simplifying the endoscope apparatus.
In addition, in the endoscope, also provided is a light emitting diode driving circuit which is a light source driving circuit for applying electric power supplied from a battery provided to the display device, for example, to the light emitting diode after adjusting the electric power to the current rating of the light emitting diode.
Incidentally, an endoscope generally has watertight structure, since the outer surface of the endoscope is cleaned after use. That is, inside of the endoscope except for an opening of a duct and the like, is occluded by an exterior member. In order to reduce the weight of the whole endoscope, the exterior member of the endoscope is usually made of plastic material.
However, if the light emitting diode emits light, and in addition, the light emitting diode driving circuit continues to be driven, for example, in an enclosed space inside the operation portion in the endoscope covered with the plastic exterior member, there is a problem such that the light emitting diode is degraded by heat radiated in the enclosed space inside the operation portion due to the light emission of the light emitting diode and the driving of the light emitting diode driving circuit, and the lifetime of the light emitting diode is shortened, since the plastic exterior member has a low heat transfer efficiency.
Therefore, conventionally, there has been a compelling circumstance to make the light emitting diode emit light with electric power lower than the rated value in consideration of heat radiation efficiency of the plastic exterior member and the lifetime of the light emitting diode.
In view of such a circumstance, Japanese Unexamined Patent Application Publication No. 9-285443 discloses an endoscope having a configuration in which a small size illumination lamp as a light source is provided in a distal end portion of an insertion portion of the endoscope, and a light emission control circuit serving as a light source driving circuit for supplying electric power to the small size illumination lamp is provided in an operation portion of the endoscope. With such a configuration, the small size illumination lamp and the light emission control circuit are provided in different spaces, so that a heat radiating position from the small size illumination lamp and a heat radiating position from the light emission control circuit are different. Therefore, in the configuration, heat radiation points are dispersed, so that heat is radiated from the whole endoscope, while preventing localized heat radiation.
In addition, Japanese Unexamined Patent Application Publication No. 2002-112953 discloses a light source device which is mounted to a light source mounting port of an operation portion of an endoscope, and the light source has such a configuration that an LED lamp as a light source and a constant current source as a light source driving circuit are disposed separately from each other. With such a configuration, a heat radiating position from the LED lamp and a heat radiating position from the constant current source are different, thereby preventing localized heat radiation.